From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Date: Tue, 10 Oct 2017 10:14:20 +0100 From: Will Deacon To: Ard Biesheuvel Cc: Bjorn Helgaas , linux-pci , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Leif Lindholm , Graeme Gregory , Bjorn Helgaas , Rob Herring Subject: Re: [PATCH v4 1/2] PCI: pci-host-generic: add support for Synopsys DesignWare RC in ECAM mode Message-ID: <20171010091419.GA5693@arm.com> References: <20171006163919.14898-1-ard.biesheuvel@linaro.org> <20171006163919.14898-2-ard.biesheuvel@linaro.org> <20171006232158.GI25517@bhelgaas-glaptop.roam.corp.google.com> <20171009164607.GD30085@arm.com> <20171010001351.GQ25517@bhelgaas-glaptop.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-ID: On Tue, Oct 10, 2017 at 10:04:03AM +0100, Ard Biesheuvel wrote: > On 10 October 2017 at 01:13, Bjorn Helgaas wrote: > > On Mon, Oct 09, 2017 at 05:46:07PM +0100, Will Deacon wrote: > >> On Fri, Oct 06, 2017 at 06:21:59PM -0500, Bjorn Helgaas wrote: > >> > On Fri, Oct 06, 2017 at 05:39:18PM +0100, Ard Biesheuvel wrote: > >> > > diff --git a/drivers/pci/host/pci-host-generic.c b/drivers/pci/host/pci-host-generic.c > >> > > index 7d709a7e0aa8..01e81a30e303 100644 > >> > > --- a/drivers/pci/host/pci-host-generic.c > >> > > +++ b/drivers/pci/host/pci-host-generic.c > >> > > @@ -35,6 +35,43 @@ static struct pci_ecam_ops gen_pci_cfg_cam_bus_ops = { > >> > > } > >> > > }; > >> > > > >> > > +static int pci_dw_ecam_config_read(struct pci_bus *bus, u32 devfn, int where, > >> > > + int size, u32 *val) > >> > > +{ > >> > > + struct pci_config_window *cfg = bus->sysdata; > >> > > + > >> > > + /* > >> > > + * The Synopsys DesignWare PCIe controller in ECAM mode will not filter > >> > > + * type 0 config TLPs sent to devices 1 and up on its downstream port, > >> > > + * resulting in devices appearing multiple times on bus 0 unless we > >> > > + * filter out those accesses here. > >> > > + */ > >> > > + if (bus->number == cfg->busr.start && PCI_SLOT(devfn) > 0) > >> > > + return PCIBIOS_DEVICE_NOT_FOUND; > >> > > >> > I think we should return 0xffffffff data here, as we do in other > >> > similar accessors (dw_pcie_rd_conf(), altera_pcie_cfg_read(), > >> > rockchip_pcie_rd_conf()). > >> > > >> > Actually, xilinx-nwl has a nice trick: it implements > >> > nwl_pcie_map_bus(), which returns NULL for invalid devices. Then it > >> > can use the generic accessors, and pci_generic_config_read() already > >> > fills in ~0 for this case. > >> > > >> > What do you think of the following? I put it on my pci/host-generic > >> > branch for now (pending your response and an ack from Will). > >> > >> I'd probably just inline the device check in pci_dw_ecam_map_bus directly, > >> but either way: > >> > >> Acked-by: Will Deacon > > > > Thanks. The reason I split out pci_dw_valid_device() is because there are > > several other *_valid_device() functions in other drivers that do basically > > the same thing, and I think it's useful to be able to see that they're all > > similar, as opposed to being buried in the config accessor or map > > functions, which vary a little more. > > > >> I'm assuming this is so small that there's no point in having a Kconfig > >> option for these guys that depends on the generic host driver? > > > > Good question; I don't care either way. > > In this case, may I suggest we leave the patch as is? Neither of you > seem to mind, and it will make /my/ life much easier, given that I > don't have to chase distros to get this driver enabled in their kernel > configs (unless we make if 'def_bool y', in which case it makes even > less sense to add the Kconfig option in the first place). Yup, I acked it as-is, just thought it was worth asking the question. Will